This invention relates to circuit breakers. More particularly, the invention relates to a snap-in panel mounted circuit breaker.
Circuit breakers of the general type to which this invention is directed are usually mounted on equipment panels. Typically, for each breaker to be mounted, the panel will have a cut-out for the breaker handle, and two adjacent screw holes aligned with corresponding threaded openings in the breaker face. Each breaker will then be individually screwed into the panel. This is a time consuming and labor intensive operation which is not well suited to maintaining cost effective manufacturing techniques, particularly in certain industries. The electronics industry, for example, uses large numbers of panel mounted breakers. Large mainframe computers usually have a breaker connected to each main circuit. Such computers will employ racks of panels containing hundreds of breakers that must be individually mounted to the panel and individually wired to the circuit it is intended to protect. It is desireable to steamline the circuit breaker mounting and wiring operations and reduce their labor intensity as much as possible.
Attempts have been made in the past to overcome the circuit breaker panel mounting and wiring difficulties discussed above. One such technique is the use of a snap-in panel mounted breaker. A snap-in mounting arrangement allows the technician to mount the breaker from the front of the panel by pressing it into an opening of a suitable size to accommodate the entire breaker casing, except for a front cover plate. Spring fingers having cammed surfaces engage the edges of the panel and lock the breaker in place when it has been pushed all the way into the opening. One such snap-in panel mounted breaker that has been commercially developed is shown in U.S. Pat. No. 3,453,408, issued July 1, 1969 to C. Mune. Other snap-in panel mounted switches are shown in U.S. Pat. No. 2,703,662, issued Mar. 8, 1955 to E. A. Meyer and U.S. Pat. No. 2,223,673, issued Dec. 3, 1940 to H. Catron et al.
One feature that is common to each of the devices shown in the Mune, Meyer, and Catron et al. patents is that the means for retaining the breaker in the panel opening are all spring clip members formed from resilient material. With the exception of one embodiment disclosed in the Mune '408 patent, the spring clips are all formed from metal stampings. This presents a problem where it is necessary to meet certain tolerance specifications on a mass production level. It is very difficult to mass produce stamped spring arm members of the type used in the assembly shown in the Mune, Meyer, and Catron et al. patents that all have the same or substantially the same resiliency within the required tolerances.
Another problem that occurs with the spring arm devices of the prior art, and particularly with the snap-in panel mounted breaker of the type shown in the Mune '408 patent, is that they are removable merely by pulling on the handle with suficient force to overcome the securing force exerted by the spring arm. This tends to dimininsh the security of the mounting of the breaker and can lead to damage to the spring arms.
The present invention provides a new and improved type of snap-in panel mount circuit breaker assembly which avoids the problems associated with prior art devices. In particular, the present invention is capable of providing a mass producible snap-in assembly that stays within required tolerance specifications and which is not subject to being pulled out of the panel merely by pulling on the handle of the breaker.